Oxide Removal Questions and Answers

Q. We always talk about removal of oxides from the surface of your base materials before plating. What is the physical reason why this must be done? 

A. You are absolutely correct. We always talk about cleaning surfaces prior to plating to remove oils, chemical films and oxides from the surface. However, we rarely give a simple description as to why this must be done. In actuality, the answer is straightforward.

The surface of your base material has to be made active which means that active bonding sites must be created on the surface. What we are really saying is that the outer electrons of the surface atoms must be available to bond with the outer electrons of the metal being deposited. This is called a chemical bond. If the outer electrons of the surface atoms are tied up with the formation of oxides, they cannot bond with the electrons of the deposited metal. Hence, a bond will not form or at best, a weaker bond will result.

You can still form a mechanical bond if the surface is suitably roughened but it is a much weaker bond compare to that of the electron bond. 

Q: We always talk about removal of oxides from the surface of your base materials before plating. What is the physical reason why this must be done?

A. Your question is not a dumb one. In many aspects of our lives, statements are accepted without question. Electroplating and metal finishing is no exception. The reason oxides are removed from surfaces to be plated is to form active sites on the surface so that the subsequent deposit will bond properly.

The strongest bonding mechanism involves bonding through the outermost electrons in the surface atoms. If these atoms have their bonding sites occupied by oxides, the bonds cannot form.

The second bonding mechanism is a mechanical or interlocking type of bond. Bonds of this type are not as strong as those formed by the outermost electrons of atoms.

In certain cases, the only type of bonding that can be achieved is mechanical bonding. This type of bonding, while adequate in some applications, is not acceptable in most cases.